1. Field of the Invention
The present invention relates to an ink jet printhead, and more particularly, to a recognition circuit for an ink jet printhead disposed on an ink jet printer.
2. Description of the Prior Art
Please refer to FIG. 1. FIG. 1 is a function block diagram for anormnal identification circuit 45 for an ink jet printer 40 disclosed by a U.S. Pat. No. 5,363,134 named xe2x80x9cIntegrated circuit print head for an ink jet printer including an integrated identification circuitxe2x80x9d by the Hewlett-Packard Company. The identification circuit 45 provides identification information about an ink jet printhead 41 disposed on an ink jet printer 40 to the printer 40. The printer 40 comprises a controller 42 and a printhead drive circuit 43. The controller 42 operates the printer 40. The drive circuit 43 drives the printhead 41. The printer 40 also comprises three busses 47A, 47B, and 47C connecting the controller 42 to the drive circuit 43. The busses 47A, 47B, and 47C transmit the controller""s 42 digital control signals to the drive circuit 43, making the drive circuit 43 output corresponding analog voltage impulses to each circuit of the printhead 41. The printhead 41 comprises an array circuit 44, which heats and then sprays ink corresponding to the output signals of the drive circuit 43, an identification circuit 45 that provides printhead identification, information to the ink jet printer 40, and a thermal sensor circuit 46 that provide""s the printhead""s temperature information to the inkjet printer 40. There are a plurality of row lines 48A (or address lines) and column lines (not shown in FIG. 1) connecting the drive circuit 43 and the array circuit 44. The drive circuit 43 selects and operates each electrical element of the array circuit 44 by these row and column lines.
Please refer to FIG. 2 and FIG. 3. FIG. 2 is a schematic diagram illustrating the array circuit 44. FIG. 3 is a circuit diagram for a resistor cell 39 shown in FIG. 2. The array circuit 44 comprises a plurality of resistor cells 39, disposed on a plurality of rows AN and columns PN, to heat and then spray an ink containerxe2x80x3xe2x80x2 ink. The plurality of rows (address lines from A0 to A5) and columns (power supply lines from P0 to P5) are connected with the array, circuit 44 to provide to or withhold from each resistor cell 39 the energy to generate heat and then spray the ink. Each resistor cell 39 comprises a resistor 33 and a transistor 34. The transistor 34, coupled with a corresponding address AN, controls current flowing via the resistor 33. When the row and column connected with the resistor cell 39 are applied a positive voltage, the transistor 34 will conduct and generate a current flow through the resistor 33. Then the resistor 33 will heat the ink, generating bubbles to spray the ink droplets.
Please refer to FIG. 4. FIG. 4 is a diagram of the identification circuit 45. The identification circuit 45 comprises a plurality of rows (address lines from A1 to A13) and programmable paths. Each programmable path comprises a fuse (F1 to F13) connected in series to a corresponding transistorxe2x80x3xe2x80x2 (Q1 to Q13) gate. Each programmable path provides a one-bit identifying code to the printer 40. The identifying code, either xe2x80x9c1xe2x80x9d or xe2x80x9c0xe2x80x9d, is determined by the state of each corresponding fuse. Each fuse state provides a different identifying code to the printer 40.
The identification circuit 45 is connected with the address lines. When voltage is applied to one of the address lines, other address lines will be affected, causing abnormal performance of the inkjet printhead 41.
It is therefore a primary objective of the claimed invention to provide a recognition circuit for an ink jet printer to solve the above mentioned problem.
According to the claimed invention, the recognition circuit provides the printhead""s identification information to the ink jet printer. The recognition circuit includes a plurality of power supply lines, a plurality of address lines, and a control circuit for operating the ink jet printer. The recognition circuit functions by applying a working voltage to the power supply lines, and applying an address voltage to the address lines. The recognition circuit also includes an identification circuit and a heating circuit having a plurality of heating cells. The heating cells connect with a corresponding power supply line and include a heating element and a switch. This switch connects in series to the heating element of the heating cell and a corresponding address line. The control circuit can turn on or turn off the switch via the corresponding address line. When the working voltage is applied to the power supply line coupled with the heating cell and the address voltage is applied to the address line coupled with the switch, the switch is turned on. A current flows from the power supply line through the heating element and the switch, causing the heating element to generate thermal energy.
The identification circuit has a plurality of identifying cells, each of the identifying cells having a first end and a second end. The first end is coupled with both the heating element and the switch of a corresponding heating cell, and the second end is coupled with a common output terminal of the identification circuit. The control circuit can determine whether any individual identifying cell is in a programmed or an un-programmed state by applying an identifying voltage to the power supply line coupled to the corresponding heating cell. The control circuit can therefore generate the identification information of the printhead by determining the states of the identifying cells.